1. Field of the Invention
The present invention relates generally to the field of electronic devices and, more specifically, the present invention relates to integrated circuits.
2. Background Information
There is currently a need in industry for a cost-effective, efficient and practical method for producing large arrays of electronic elements that can provide, produce or detect voltages. One example of such a need is that of displays, where each voltage becomes a subpixel intensity. Flat panel displays (FPDs) have become a multibillion dollar industry and is presently a growing portion of the high-resolution display market, which is itself growing rapidly. Liquid crystal displays (LCDs) dominate the FPD marketplace. One type of FPD is the active matrix LCDs or active matrix displays. Active matrix displays have a substantial worldwide infrastructure and are a proven commercial technology.
Each picture element or pixel of an active matrix LCD contains one or more thin film transistors. The presence of these active elements make it possible to more clearly and precisely control the brightness of each pixel, which dramatically improves the quality of the display. The advantages of active matrix LCDs become more pronounced as the screen sizes and resolutions increase. However, as screen sizes and resolutions increase, the manufacture and production of active matrix LCDs become increasingly difficult because is challenging to produce active matrix LCDs with high yields. For example, if a particular active matrix LCD has an unacceptably large number of defects, such as for example defective transistors or pixels, the entire active matrix LCD is discarded even though a relatively small number of elements are defective compared to the total number of elements on the active matrix LCD.
One concern with the increasing size of large arrays of electronic elements is that as the number of electronic elements in the array increases, the lower the probability that all of elements in the array will work properly. With existing techniques, it is difficult to test any of the elements until the assembly is complete. If there are imperfections in the array, the imperfections must be tolerated. Otherwise, the entire array must be discarded, or special and expensive techniques must be used to repair the imperfections in the array.
Silicon very large scale integration (VLSI) processes may be used to produce an array of electronic elements over a silicon wafer surface. A disadvantage with using these processes is that silicon wafers are conductive, limited in size and are generally not transparent. Furthermore, large areas of processed silicon wafers can be expensive. In particular, displays that valve the light coming through them need to be largely transparent. Single crystal silicon can be bonded to a glass substrate, and then etched to remove most of the area to achieve transparency, but this is intrinsically wasteful in that, for the sake of maximizing light transmission, the majority of the processed material is discarded, and becomes chemical waste. The underutilization of the precious die area wastes resources, causes greater amounts of chemical waste to be generated in the process, and is generally inefficient and expensive.
There are of course countless other examples of arrays of electronic elements that have useful applications. Another example of such an array is a photodiode array to collect solar energy. Large arrays of silicon photodiodes with concentrating lenses have been made by sawing wafers and using pick and place assembly, but thermal dissipation is poor for large elements, and small elements required too much assembly time.
Thus, what is desired are methods and apparatuses for fabricating and testing arrays of electronic elements.